Prescription opioid supply-restricting policies and hospital use by people prescribed opioid medications, Victoria, 2018-22: a controlled interrupted time series analysis.

Objectives: To investigate the combined effect of two policies for reducing prescription opioid supply in Australia on hospital use by people prescribed opioids in primary care.

Study design: Retrospective data linkage study; controlled interrupted time series analysis of linked primary care electronic medication records and hospital admissions data.

Setting: Three Victorian health care networks (Monash Health, Eastern Health, Peninsula Health); pre-intervention period: 1 April 2018 - 31 March 2020; intervention period: 1 April 2020 - 31 March 2022.

Participants: People prescribed opioid medications at least twice during the preceding six months (opioid group) and propensity score-matched patients, based on age, gender, comorbidity, and residential postcode-based socio-economic status (control group); matching was undertaken for each month of the study period.

Intervention: Mandatory prescription drug monitoring (from 1 April 2020); tighter restriction criteria for the subsidisation of opioid medications by the Pharmaceutical Benefits Scheme (PBS) (from 1 June 2020).

Main outcome measures: Differences between the opioid and control groups in immediate changes after start of the intervention in rates of emergency department (ED) presentation and hospital admission related to opioid use, non-opioid substance use, self-harm, or mental health problems; differences between the two groups in the change in trend for these rates between the pre-intervention and intervention periods.

Results: Propensity matching was undertaken for 179 091 people in the opioid group and a total of 389 061 people in the control group. The opioid-related ED presentation rate for the opioid group had been increasing prior to the intervention, but declined after its introduction at a rate not significantly different from that of the control group. The immediate change in non-opioid substance-related ED presentation rate was greater for the opioid group than the control group (β, 11.1 [95% confidence interval, 1.7-20.5] presentations per 100 000 patients); by 31 March 2022, the rate had declined to below the pre-intervention level. Differences between groups in changes to self-harm- and mental health-related presentations, and in all hospital admission rates, were not statistically significant.

Conclusion: Following implementation of two prescription opioid supply-restricting polices in 2020, the opioid-related ED presentation rate declined among people prescribed opioids; the non-opioid substance-related presentation rate initially increased, but was lower than the pre-intervention level by the end of the study period. Our findings suggest that some opioid-restricting policies can reduce opioid-related harm without increasing long term non-opioid substance- or mental health-related harm.

Study registration: European post-authorisation study register (EUROPAS), EUPAS104005 (prospective).